Enamel is the first and main line of defense against dental decay, and its proper formation is a prerequisite for strong, healthy teeth. Abnormalities in the molecular and cellular pathways that drive enamel formation (amelogenesis) result in amelogenesis imperfecta, a broad designation for a number of non-syndromic and syndromic enamel defects. A better mechanistic understanding of amelogenesis is important to devise new and improved strategies in the prevention, diagnosis, and treatment of dental caries and inherited disorders such as amelogenesis imperfecta. Because enamel is unique amongst mineralized tissues in its epithelial origin, genes involved in epithelial development and integrity such as Perp are excellent candidate regulators of amelogenesis. PERP (P53-effector related to PMP-22) is a membrane protein that plays an essential role in the stable assembly of desmosomes, which are cell-cell adhesion macromolecules central to epithelial integrity and homeostasis. I have recently found that inactivation of Perp leads to enamel defects, in part, due to the detachment of ameloblasts from the underlying stratum intermedium (SI) layer. The ameloblast-SI interface is an area of co-localization between PERP and desmosomes, and high magnification images revealed desmosomal defects. In addition, a large number of differentially regulated genes in the teeth of Perp-null mice were identified. Several of these genes are previously characterized regulators of amelogenesis but the majority has never been shown to play a role in this process. Beyond my initial studies, little is known about the function and regulation of Perp in amelogenesis. In this application, I propose to test the hypothesis that the function and regulation of Perp play a central role in amelogenesis. This will be done by the analyses of antibody-treated mice and various mouse genetic models, as well as experiments using cell culture. Successful completion of these studies is important for issues of human oral health related to proper tooth development.